Rockwell Automation 1336 8A-48A Fiber Industry - Manual (Page 19)

2–11 Installation/Wiring
Motor Cables
A variety of cable types are acceptable for drive installations. For
many installations, unshielded cable is adequate, provided it can be
separated from sensitive circuits. As an approximate guide, allow a
spacing of 0.3 meters (1 foot) for every 10 meters (32.8 feet) of
length. In all cases, long parallel runs must be avoided. Do not use
cable with an insulation thickness less than or equal to 15 mils.
The cable should be 4-conductor with the ground lead being
connected directly to the drive ground terminal (PE) and the motor
frame ground terminal.
Shielded Cable
Shielded cable is recommended if sensitive circuits or devices are
connected or mounted to the machinery driven by the motor. The
shield must be connected to both the drive ground (drive end) and
motor frame ground (motor end). The connection must be made at
both ends to minimize interference.
If cable trays or large conduits are to be used to distribute the motor
leads for multiple drives, shielded cable is recommended to reduce
or capture the noise from the motor leads and minimize “cross
coupling” of noise between the leads of different drives. The shield
should be connected to the ground connections at both the motor and
drive end.
Armored cable also provides effective shielding. Ideally it should be
grounded only at the drive (PE) and motor frame. Some armored
cable has a PVC coating over the armor to prevent incidental contact
with grounded structure. If, due to the type of connector, the armor is
grounded at the cabinet entrance, shielded cable should be used
within the cabinet if power leads will be run close to control signals.
In some hazardous environments it is not permissible to ground both
ends of the cable armor because of the possibility of high current
circulating at the input frequency if the ground loop is cut by a
strong magnetic field. This only applies in the proximity of powerful
electrical machines. In such cases, consult factory for specific
guidelines.